The present invention relates to engine motion restrictors for vehicles, and to vehicles including such engine motion restrictors.
More particularly, the invention relates to an engine motion restrictor for limiting movements of a vehicle engine relative to a vehicle structure (vehicle frame and/or vehicle body) on which said engine is mounted, said engine motion restrictor including:
first and second rigid strength members, one of said strength members being designed to be fixed to the engine and the other strength member being designed to be fixed to the vehicle structure,
a mechanical link member connecting said first strength member to said second strength member,
and at least an elastomer mount interposed between said first strength member and the link member (optionally, an additional elastomer mount could be interposed between the second strength member and the link member).
In known engine motion restrictors, as disclosed for instance in U.S. Pat. No. 5,364,061, the two strength members are constituted by metal bushings which are respectively surrounded by two elastomer mounts, said elastomer mounts being connected to a rigid link rod constituting said link member.
These known engine restrictors are generally satisfactory, but may however experience the following drawbacks:
their stiffness perpendicularly to the longitudinal direction of the link rod may generally not be cut down to very low values, at a reasonable cost,
the link rod may experience resonance phenomena at certain speeds of the engine, which generates noises or other vibrations transmitted between the engine and the vehicle structure,
and it is difficult to design the rigid link rod so that it may collapse under a collision event, as it is sometimes required by carmakers.
An object of the present invention is to overcome these drawbacks.
To this end, according to the invention, in an engine motion restrictor of the above type, the mechanical link includes an intermediate rigid member and a flexible cable which connects said intermediate member to said second strength member, said elastomer mount being interposed between said first strength member and said intermediate member.
This engine motion restrictor may be mounted so as to:
be in tension when the engine generates a torque in normal driving condition, in which case the engine motion restrictor effectively restricts the rolling motion to which the engine is subjected,
and enable free movement of the engine when the vehicle operates in reverse.
The design of the engine motion restrictor according to the invention enables to reduce forces transmitted from the engine to the vehicle structure in directions perpendicular to the direction of the cable. This eliminates some eigen modes of resonance experienced by common engine motion restrictor designs.
Further, the invention may allow for very low stiffness values at idle by incorporating slack in the cable under low torque produced by the engine, which then results in good vibration isolation.
Alternatively, some preload may be applied to the cable under idle, providing stiffness under some reverse loading conditions.
Besides, since the cable has negligible stiffness in compression, the engine motion restrictor may collapse in the event of a collision, thus improving energy absorption.
Additionally, the invention provides cost and weight benefits over conventional designs due to the possible use of only one molding, and elimination of a rigid link rod.
Further, only a small and versatile package space is required for the engine motion restrictor according to the invention.
In preferred embodiments of the engine motion restrictor according to the invention, one or several of the following additional features may possibly be used:
the first strength member includes a housing having at least a bottom and two parallel side walls which extend substantially parallel to the cable from said bottom toward said cable, the intermediate member being situated at least partly between said side walls, and the elastomer mount including at least two elastomer arms which extend in mutually opposite directions, each between an inner end and an outer end, the inner end of each elastomer arm being fixed to the intermediate member and the outer end of each elastomer arm being fixed to one of the side walls of the housing;
the two elastomer arms diverge slantwise from their inner ends toward their outer ends, the elastomer mount thus having a V shape which is open toward the cable;
each side wall of the housing extends from said bottom to a free end which is extended toward the intermediate member by a rigid wing, the two rigid wings of the housing being designed to cooperate by abutment with the two elastomer arms to limit movements of the intermediate member away from the bottom of said housing;
the intermediate member includes a plate having two faces substantially parallel to the side walls of the housing, each face of the plate being adhered to the inner end of one of the elastomer arms;
the plate of the intermediate member includes two rigid tabs near the bottom of the housing, said tabs of the plate being folded substantially parallel to said bottom;
a bolt is fixed to the bottom of the housing, said bolt extending outwardly from the housing;
the intermediate member is fixed to the cable by crimping;
the second strength member includes an eyelet and is fixed to the cable by crimping.
Besides, another object of the invention is a vehicle including an engine supported on a vehicle structure (vehicle frame and/or vehicle body), said engine being connected to the vehicle structure through at least an engine motion restrictor for limiting movements of said engine relative to said vehicle, said engine motion restrictor including:
first and second rigid strength members, one of said strength members being fixed to the engine and the other strength member being fixed to the vehicle structure,
a link member connecting said first strength member to said second strength member,
and at least an elastomer mount interposed between said first strength member and the link member (optionally, an additional elastomer mount could be interposed between the second strength member and the link member),
wherein the link member includes an intermediate rigid member and a flexible cable which connects said intermediate member to said second strength member, said elastomer mount being interposed between said first strength member and said intermediate member.
In preferred embodiments of the vehicle according to the invention, one or several of the following additional features may possibly be used:
the first strength member is fixed to the vehicle structure and the second strength member is fixed to the engine;
the engine motion restrictor is mounted so as to be in tension when the engine generates at least a predetermined torque (said predetermined torque may possibly be 0) in normal driving condition, and so as to enable free movement of the engine when the vehicle operates in reverse;
the cable is dimensioned to be slack when the engine operates under idle;
the cable is dimensioned to be in tension when the engine operates under idle.